Method of reforming gaseous hydrocarbons



Jan. 12, 1954 J. H. TAUSSIG, JR

METHOD OF REFORMING GASEOUS HYDROCARBONS Filed Oct. 31. 1949 PatentedJan. 12, 1954 23:65am n statt HYDROCARBONS Jenn Hawl'y Taiissig, Jr.,Ambler, Pa'.,- assignoi';

by means assignments, to The United Gas Impro'vement Company,Philadelphia, Pa; a corporation of Pennsylvania assesses casts $51,1949', seal Nb. 12i;64's

The present reverie-manta;some production of a suitable, meni c s;rbrsist iputiofiin city gas rnains',' frorn seous hydrocarbonrfiaterial. More par N cularly fiit relates to a cyclic processcomprising a re ac'tioii between a gaseous id rbb d: sr ikn wn' a teamate um tism" o a e iym is rich fr hydrogen and; Q do if carbonyinainl'ycarbon mo o fiae idit heg p-r te nr ichnientvvith' a hydroc i1 gas;can'beinade interha e ble h n? i manufacturedgases t'ubuted'm ty gasmans. Natural gas, on of most common gaseous hydrogenoas mg of increasingavaiie ability and inf foca re la'tively close' to the natural gas fieldthe gas is used iniits original as covered, the various burning ed andadjusted for its use ore nonecessit'y for treating gas; In localities,howe er,

able; ensus h ping a pliances suc s t e binners on gas iar 's",refrigerators andheating services; have beeadesfigned and adjusted iothe burning of ome wat r manuiactured gas, for instance vvateif gas ocoke oven gas. If an attempt werelto b Inade tol intro duce natural gasby itself to ajsy 7. m q ed w i a e ia es and burners design are dju tviQr n f r tured gas, its slo vver burning characteristics, if

ability of natural gas as a source of supply for the distributionsystems of the public senator'spaniesfor dcmesticaiid' industrial use,has presented the problem of reforming or converting natural gas intoaproduot' with suitable charaic o teristics to enable its use asacompcnent of mixed gas'for distribution with frnanufactured'gas in citygas mains. The" desirability of reforming to develop suitable burn gcharacteristics also applies to other gaseoushydro'carbons such asethane; ethylene,'-propane, butaneand the like, and hydrocarbon 'ic'h essuch'aslrefinery g 'as'.

Heretofore; the were mm'g of aga'seous' hydro;

vvheie natural gas lias not previously been availl6 cams; (01. 48-196) 2V v carbonhas been accomplished for the most part by passing it'througha cole fire, preferably with process steam admjixed l In this Way,thermal cracking occurs ith the formation of. hydrogen and carbon.Little or none of the carbon content of the gaseous hydrocarbonhoWe'venQis cone verted' direotly to carbon monoxide in theyapor phase,although some oi the deposited carbon may be converted to carborimonoxideand'hydro; gen byre'a'ction of the steam with the hot coke firebed. Generally, however, the carbonwhich is depoisted in the iue'Lbe'd',is consumed when blasting the fire, "on the, other hand, the oarhonwhich' pa sco twiu l th ega's cibgs the'g s mains and condensingapparatus an'eimustQ e scrubbed from the gas byiwater spraysorjpr v Gii'itated electrically, at eonsmemme added expense. v Furthermore, suchcarbon is obviously lost totheg 'a'sfmakingprocess. I v s lt' is kh'ownmate-sa as hydrocarbons can be amwwhs am lib ia e ro nan at the sametime ior n carbon monoxidebyunion of t e r n o th hyd arb a w th $116 yen. of e. ste m a i a n o ad tiona hydrogen from thesteam, but theprocesses avail b e ha o se sed cer ain d sad a t e Fo am lenca al s sch e be n mp y d to permit the reaction to tak placeat a temperaturebelowthat at which thermal cracking occurs, in order to avoid production ofoarbonas anend product. Th equipment hithertouused .forcatalytic con;-version of thehydrocarbOnsvvith steam is very costly. It, hasmainly-consisted of high alloy metal tubes or retorts filled Withcatalytic mate! rial heatefdtcxternally in a furnace.The'hydrocarbongases' vandsteam are. passed through the: catalyticmaterial continuously with production of hydrogemcarbo'n monoxide, andsmall amounts of carbon dioxide. Aslstated, the process COIIP, ducted insuch equipment hascerta'in disadvan tagesu Thus the'temperature of thecatalyst is maintained by conduction of the heatfrom' the furnace,through the tubes, to supply the heat-of formation of the product as.and'its's'e'ns'ible heat; The conductivity of the catalytic material indiscrete particle form not high so that the metallic tubes orretor't'sif the catalysti's held at a high-temperature of, for exsmme;from 16G0 F. 1s0o mus-separate at a temperature not've'ry' far easemaximum s'afe' tiripera-v tiire of the 'mo's't' resistant metalnoyjtub's afii necessaril higher than't'n peace-Lori temper v of'the'cataly'sti urthermore, since the cond 0- tion from; particle topal-tine of the catalyst 1 poor; tem erature or the catalyst next t6"the tube or retort wall is higher than at the center, making anon-uniform temperature across the tube or retort. In addition, not onlyare the high alloy metal tubes expensive and subject to considerablemaintenance costs but the multiplicity of tubes requires a multiplicityof valve connections and flowmeters which in turn add to the expense ofinstallation.

Because of these difficulties, inherent in a continuous, externallyheated reforming system, various cyclic processes have been suggestedfrom time to time. One such process involved the use of a catalyst bedwhich was alternately blasted with burning gases to store heatin thecatalyst followed by passing the gaseous hydrocarbon and steam throughthe bed to effect conversion. However, by this method, in order to avoiddestruction of the catalyst bed by excessive'combustion temperatures,the quantity of heat stored in the catalyst bed was limited with theresult that the incoming cooler steam and hydrocarbon gas, coupled withthe high heat requirements of the reforming reaction itself rapidlycooled the catalyst to below reaction temperatures and caused wide andrapid fluctuations in temperature. Also since the heat required forraising the reactants to reaction temperature and for the resultingendothermic reaction, was supplied by the heat stored in the catalystbed, excessively large amounts of catalyst, a very expensive item, wererequired. In addition, in many of these prior cyclic processes,relatively large amounts of carbon and other combustible materials weredeposited on the catalyst which decreased its activity and clogged. thegas passages through the catalyst bed.

One object of the present invention is to provide a process for thetreatment of gaseous hydrocarbon material, particularly natural gas, andsteam to produce a component of a combustible gas which can serve as asource of gas for distribution in city mains and where manufactured gashas previously been supplied, which process does not possess thedisadvantages of either the thermal cracking process or the catalyticconversion processes presently known.

A further object of the invention is to provide a process by whichnatural gas can be economically and efficiently converted into a cleangas, rich in free hydrogen and in which the carbon content of thehydrocarbon reacted is present in gaseous form, mainly as carbonmonoxide, and in which no significant amount of free carbon or othersolid combustible matter is formed during the process.

Still another object of the invention is to furnish a method for theproduction of a combustible gas which is free from carbon particles andis available for admixture with other gas to provide a gaseous productwhich will be interchangeable with manufactured water gas or coke ovengas in the distribution systems of the public utility companies.

A further object of the invention is to provide a relatively inexpensiveapparatus of high capacity for the process described and of a design towhich existing gas-making equipment can be of the cycle.

tion also. As the result of the reformation or conversion reaction, agas rich in free hydrogen and containing carbon in the form of gaseousoxides, mainly carbon monoxide, will be obtained.

The process involves the use of a cycle having a heat storage portion orstage in which hot combustion gases, formed by the combustion of a fluidfuel, are swept through a path of heat storage material and then througha bed of reforming catalyst, that is a catalyst for the endothermicreaction between gaseous hydrocarbons and steam, heating the heatstorage material and catalyst by direct contact with combustion gases;and a reforming portion or stage in which the gaseous reactants, that ishydrocarbon gas and steam, or hydrocarbon gas, steam and air, are heatedin the path of heat storage material and then reacted in the presence ofthe catalyst. Such a procedure may be designated as a cyclic process.Thus, in one part of the cycle fluid fuel is burned in a combustionchamber and the hot products of combustion are passed through a zonefilled with heat storage material and then through a zone of catalyst tostore heat therein and to supply the heat required for the process. Inthe other part of the cycle, the reacting hydrocarbon gas mixed withsteam, and, in the preferred embodiment with air, is conducted firstthrough the zone containing heat storage material, which serves as apreheating zone, to raise the temperature of the mixture to the reactingtemperature, and then through the zone containing the catalyst in whichthe reaction takes place, producing a clean gas in which the hydrogen ofthe reacting hydrocarbon has been liberated and the carbon thereof hasbeen combined with the oxygen in the steam (and of the air if air isused) to form carbon monoxide and carbon dioxide. It will be seen thatbefore the reactants are brought in contact with the catalyst they areblended and uniformly preheated in a preheating zone containing the heatstorage material which in turn is heated by the combustion gases in theheat storage portion As will be more fully discussed hereinafter, beforedistribution as city gas the gas produced during the reforming portionof the cycle will have mixed therewith a predetermined portion ofnormally gaseous hydrocarbon in order to provide the desired calorificvalue.

The process also comprises certain advantageous features whereby the hotproducts of combustion utilized for storing heat during the heat storageportion of the cycle are so controlled as to maintain the catalyst in ahigh state of activity, and wherein products of combustion,advantageously products of incomplete combustion, formed during the heatstorage period, are mixed in controlled amount with the reformed gasproduced during the reforming portion of the cycle, to provide a gasmixture possessing characteristics suitable for distribution indistricts supplied with manufactured gas upon enrichment withhydrocarbon gas.

Since, in the process of the present invention, the heating step isinternal as regards the heat storage and catalyst beds, no expensiveexternally heated tubes or retorts are needed to contain the catalyst,and one or two large vessels lined with refractory to contain thecombustion chamber, the heat storage space, and the catalyst bed willsufiice to provide a high capacity installation. Also, since thecombustion gases and reacting gases follow the same paths in the samedirection during their respective portions of the cycle, no

as cacao:

expensive hot valves are required which have given riseto numerousproblemsin. certain past A few large pipes will.

gas-producing systems. replace the manifoldswith the multipleconnections necessary for the tubeor retort-style plant. The controlsare likewise simplified and the cyclic changing of valves can beoperated by the automatic control method established for many years inthe water gas art. Furthermore, the cyclic system is more susceptible tothermal control because the temperatures can be regulated in a fewminutes in contradistinction to the continuously fired' tube or retortfurnace, for instance, which requires considerable time to effectdesired.

changes. Since the reactants are preheated. to

matically an apparatus in which the process of the. present inventioncan be carried out.

In the drawing, 1 represents a refractory-lined chamber which may be thesuperheater of a conventional water gasset with appropriatemodificationas. is obvious: from the drawing- 2 represents thecombustion chamber which may be nothing more than a space preceding theheat storage zone 3'. Heat storage. zone 3 consists of heat.-accumulating refractory bodies such as fire brick arranged in'familiarcheckerwork pattern, laser. randomly arranged-pieces of refractory ma.-terial,v [5,.01', as thedrawing indicates, a combination .ofboth. Theheat storage. material may besupportedgas by. fire brick arch it: Theheat storage-zone L advantageously consists of layers ofdifferentrefractory pieces supported upon a checlrerwork arch; the pieces nearerthe checkerworl: beingrelatively coarse pieces andsupportingna; deeperlayer of smaller pieces advantaeously of. material of high heatconductivity, such as bonded silicon carbide, and the like: Thecatalyst. bed is represented by 5, and maybe. sup;-

ported as by firebrick arch H. Numerals 5 andac' represent respectivelythe air andfiuid fuel supply-means for combustion to heat theap-paratus,and i the'stack valve through which-the waste heating gases may bedischargedto theatmos phere, orto a waste heat boiler (notshcwn), be--fore being vented to the atmosphere. The entrance for the gaseoushydrocarbonreactantand steamfor introduction into the re-heating zoneat. a. position adjacent the combustion zone so that the. reactantspassthroug-h the preheating bed and catalyst bedin'the same direction'asthe hotproducts of combustion, arerepresented-oy t.

and t respectively, and the entrance for process air-,: if used,- atIii. through which gas leaves the reactionchamber, passing-throughwashbox l2 to storage by concluit; 53.- In accordance with knowngaspractice, the gases leaving the reaction chamber or; stor-- age-maypassthrough a .waste heat boiler (not shown); before reaching the: washbox.

The operation is,. as. stated; cyclic and the process, comprisesfirst:a= heating.- or blasting I i represents the conduitreactiontemperatures prior to reaching the cataly stbed, wide andrapidfluctuations in catalyst 6-; period-during which air and-a-fiuidrareadmitted: through connections 5 and 6,. respectively, cornbustion taking place in the combustion chamber 2. The hot combustiongases are passed through the preheating or heat storagezone3-whichraises it to a temperature above the temperature required for thereformation reaction, are then passed through the catalyst bed at a"-somewhatreduced temperature, and-may then be dischargedthrough stackvalve 7'. After the set is heatedto operating temperature, thestackvalve 1 is:

closed and air and fuel connections 5' and-6 are also closed. At thesame time, connections 8 and 9 are opened to admit respectively thegaseous hydrocarbon and the process steam to react with.

After leaving the preheating or heat storage zone,

the reaction gases enter thecatalyst bed.- where the following typicalreactions take place (when natural gas is being reformed) (2) with air,

1.9N2-I-13l95 B. t. u. per lb. m'ol While the drawing illustratesoneshelL-itwill be understood that a two or three shell set-may.

be employed following the same generalprinciples described above. Forinstance, the carburettor and superheater shells of a'conventional car--buretted water gas set may be employed. These shells are connected attheir bases by an-- open conduit. In practicing the present process inthis arrangement the fuel and air can be admitted to the top of thecarburetter where combustioir takes place, the hot products ofcombustion passing down through the carburetter, through the connectingconduit to the superheater andupv through the preheating and catalystzones as described. Similarly, in such anarrangement, the gaseoushydrocarbon reactant, steam, process air if used, can be admitted to thecarburetter top passing down through the carburetter, through theconnecting conduit to theba-se of the superheater and up through thepreheating and catalyst zones as described. Any checker work in thecarburetter shell will function as-part of the preheating zone.Similarly, in a three shell arrangement, employing also the generatorof'a conventional carburetted water gas set, the generator. may serve ascombustion chamber, and the various materials can be admitted. to thegenerator, flowing to the ca'rburettertop by way of the open conduitconnecting the tops of the generator and carburetter, thence to thesuperheater as described.

In addition, it will berealizedthat in accordance with common gas-makingpractice steam purges may be, and preferably are, made between theheating and the gas-generating. portions of the cycle, or between thegas-generating and heating portions of the cycle, orboth. These andmaking art, serve to clear the system of undesirable gases which maycontaminate the generated gas or serve to force residual desirable gasesto storage.

Catalysts for the endothermic reaction of gaseous hydrocarbons withsteam to produce gas mixtures comprising free hydrogen and carbonmonoxide, together with variable proportions of carbon dioxide, arewell-known. The catalysts most frequently proposed for this purpose aremetals of the iron group, with nickel and cobalt catalysts usuallypreferred, although other high melting metals such as vanadium,chromium, platinum and the like have been used. As between nickel andcobalt, the nickel catalysts have usually been used because the reactionis easier to control and the nickel catalysts are less expensive.

A suitable refractory carrier is frequently employed, on the surface ofwhich the catalytic material is disposed or throughout which it isdistributed. Difficultly reducible oxides such as alumina, silica,magnesia, calcium oxide, titanium oxide, chromium oxide, oxides of rareearth metals such as, for example, thoria, ceria and/or others may bepresent. Compounds such as chromates may be employed.

One method of catalyst preparation involves the precipitation of thecatalyst in the form of a salt upon finely divided carrier material,calcination to produce the oxide of the catalyst metal, pelleting or themaking of extruded shapes from a paste of the calcined material, andreduction of the oxide at elevated temperature to the metallic catalyst,either as a step in the preparation of the catalyst or after it has beenplaced in the gastreating equipment. In the preparation of another typeof catalyst, preformed refractory bodies, such as alundum balls, and thelike are impregnated with a salt of the catalytic metal and thereafterthe impregnated shapes are calcined to form the oxide of the metal whichis subsequently reduced. The catalyst employed may be produced by anydesired procedure which forms no part of this invention.

The gaseous hydrocarbon material reformed in the gas-generating portionof the cycle may comprise normally gaseous hydrocarbon material such,for example, as methane, ethane, propane and/or butane. Correspondingunsaturated hydrocarbons may be present in any desired concentration,such, for example, as ethylene, propylene, butylene, etc. Otherconditions being the same, saturated hydrocarbon material is preferred,with paraflinic material most preferred. Natural gas, which is primarilymethane and refinery oil gas, which is primarily methane and ethyleneare among the hydrocarbon materials which may be employed. Natural gas,because of its availability is particularly preferred as the hydrocarbonreactant.

With respect to the fuel employed during the heat-storage period of thecycle, it may be any fluidthat is gaseous or liquid-combustible. Gaseoushydrocarbons, such as those mentioned above, and especially natural gas,are particularly satisfactory, although gaseous fuel not rich inhydrocarbons, such as water gas, producer gas, and the like may also beused. Liquid hydrocarbons, such as fuel oil, gas oil, gasoline,kerosene, tar, and the like may be employed if desired. In the event aliquid fuel is employed, conventional spraying or other vaporizing meansmay be utilized to facilitate combustion.

The proportions of gaseous hydrocarbon reactant to steam employed duringthe reforming portion of the cycle generally run between about .8 moland about 5 mols, and preferably between about 1.5 and about 2.5 mols,of steam for each mol of carbon in the hydrocarbon reactant.

3 When air is employed during the reforming portion of the cycle, theproportion of steam to hydrocarbon required may be decreased in whichcase as low as about .8 mol of steam per mol of carbon in the gaseoushydrocarbon reactant may be employed.

As stated, in accordance with the preferred embodiment of the process,some air is employed during the reforming portion of the cycle. Theamount of air so employed will be less than about 2 mols thereof per molof carbon in the gaseous hydrocarbon reactant and in most cases will beless than about 1 mol thereof per mol of carbon in the reactant.Preferably, the amount of air employed during the reforming portion ofthe cycle is between about .1 and about .6 mol thereof per mol of carbonin the hydrocarbon reactant.

Referring to the temperature conditions employed during the cycle, thereactants, as stated,

; must be heated substantially to reacting temperatures by their passagethrough the heat storage zone and before they pass through the catalystzone. The main considerations, therefore, are that the gaseoushydrocarbon reactant, while being heated sufficiently to efliectsubstantially complete reaction thereof in the catalyst zone, is notheated to a point where significant thermal cracking thereof takes placewith formation of any significant quantity of carbon in the preheatingzone. The exact temperature conditions governing these considerationswill depend in part upon the particular gaseous hydrocarbon reactantemployed. It has been found, for example, that, when reforming naturalgas, the average temperature of the heat storage material in thepreheating zone should not exceed about 2000 F., nor should it fallbelow about 1400 F. In other words, the heat storage material will havean average temperature at the beginning of the reforming portion of thecycle of not over about 2000 F., and, at the end of the reformingportion of the cycle, of not less than about 1400 F. To insure areforming run of reasonable length, when reforming natural gas, theaverage temperature of the heat storage material, at the beginning ofthe reforming portion of the cycle will not be less than about 1500 F.Because of the direction of flow of the hot combustion gases during theheat storage portion of the cycle, first through heat storage materialthen through the catalyst zone, the temperature of the catalyst, at anyone time, will normally be somewhat less than the average temperature ofthe preheat bed, and generally the temperatures in the catalyst bed, atthe beginning of the reforming run, when reforming natural gas andreferring to the above temperature ranges, will not exceed about 1800 F.and may be as low as about 1300 F. When reforming gaseous hydrocarbonsheavier than methane it may be desirable to employ somewhat lowertemperatures in the preheating zone in order to avoid thermal crackingand since the reformation of hydrocarbons heavier than methane, may notrequire temperatures as high as when methane is reformed. Thus, whenreforming hydrocarbons heavier than methane, temperatures as low asabout 1000 F. may be employed in the preheating zone.

Referring more particularly to the heat storapes-eve ageportion of thecycle of "the present process, it is conducted, as stated,'by"burninga-fiuid fuel, and passing the hot :products of combustion seriallythrough the .heat storage zone and catalyst zone. The heat storageportion of the cycle may be conducted by burning the fuel with excessair, with insufficient-air to support complete combustion, .or withjust'the amount theoretically required for complete combustion, so longas the heat storage material and catalyst are raised to the requiredtemperatures. .In accordance with a preferred embodiment of the process,however, at least the latter part of the heating portion of the cycle isconducted by burning the fuel with insufficient air to support completecombustion, thereby producing combustion products substantially devoidof free oxygen and having a substantial content of hydrogen and carbonmonoxide in addition to their content of carbon dioxide, water vaporandnitrogen. This insures the maintenance of the catalyst in a highlyactive state. The amount of air employed during this type of heatstorage operation will usually be less than 95% of that theoreticallyrequired for complete combustion of the particular fuel and may be aslow as about 70% of that required for complete combustion. The resultingcombustion products supply heat to the heat storage material and to thecatalyst by direct contact therewith without danger of oxidizing themetal catalyst. Preferably, the combustion during this type of heatstorage operation is sufficiently incomplete so as to produce combustionproducts which are reducing with respect to the oxide of the metalcatalyst, in Order to favor the presence, at the start o'fthe reformingportion of the cycle, of contact surfaces of highly active elementalmetal catalyst rather than the oxide, while ;at the same time obtaininga practical efliciency in the use of the fuel. Thus the amount of airemployed during this type of heat storage operation is preferablybetween about 85% and about93% of that theoretically required forcomplete combustion of the particular fuel employed.

As indi ated above, in accordance with a preferred form of operation of:the present process at least the latter .partof the heat storageportion of the cycle is conducted by burning the fuel with insufficientair .forcomplete combustion. 'While the entire heat storage period'maybe conducted in such a manner, it is particularly pre: ferred to conductthe first part of the heat storage period byhurning the fuel with excessair so that the combustion gases contain free oxygen, and the latterpart by burning the fuel with .insuihcient air for complete combustionas de scribed. In this case, the amount of air employed during the firstpart of the heat storage period will usually be at least 2% in excess ofthat required for complete combustionof the fuel, and may in some casesbe as high vasabout 50% in excess of that required for completecombustion. In most cases, excess air in an amount between about 5% andabout 15% of that theoretically required for complete combustion of thefuel is satisfactory. The reasons for a heat storage stage in whichexcess air is employed are to obtain maximum efficiency of combustion,to shorten the flame and thus to obtain greater heat release in thecombustion zone, and also to insure that'any trace of. combustiblematter that may have been accidentally deposited on therefractory'material and catalyst is removed. Howzever,iby.the presentprocess, as stated, very little,

it a if any, combustible matter is so deposited. '(irenerally, theheat-storage stage, in "this two-stage heat storage period, in whichexcess airis "employed may make up between about 15% and about 50% ofthe total heat storage portion of the cycle. The remainder of the heatstorage portion of the cycle;will, in this type operation, be the stageduring which insufiicie'nt air for complete combustion is employed'asdescribed.

Referring to the gas produced during the reforming portion of the cycleit will chiefly comprise hydrogen and carbon monoxide with man butvarying amounts of gaseous hydrocarbons and carbon dioxide'and withvarying amounts of nitrogen depending upon the amount of air em'-ployed'during the reforming portion of the" cycle. While this gas iscombustible it does'not possess the characteristics which would make itusable per se as city gas. For instance, it calorificvalue will be lowerthan that required for utilization'in citygas distribution systems. Thusbefore the gas produced duringithe reforming portion ofthe cycle isdistributed as city gas it must beenriched with gas having a calorificvalue higher than that desired .in the mixed gas. Such enriching gas maybe any of the gaseous hydrocarbons mentioned aboveand.particularly'natural gas.

In many cases, however, the mere enrichment of the gas produced duringthe reforming portion of the present process with a gas of highercalorific value does not provide a mixed .gas possessing all thecharacteristics required in 'a particular area. For instance, while a'mixed gas possessing the desired calorific value may be obtained bymixing, for example, natural gas with the gas produced during thereforming-portion of the present process, the specific gravity of themixed gas may still be below, and/or the ratio of hydrogen to inertsabove, the specifications in a particular area. Or, because of itsavailab-ilityin a particular area, it may be desirable to utilize cokeoven gas as part of the distributed'gas. Since coke oven gas. isrelatively rich in hydrogen, its admixture with the .gas produced duringthe reforming portion of the present process, which is also rich inhydrogen, would result in a ratio of hydrogen to inerts well above thatrequired.

.For these reasons, it is often desirable to also mix with the gasproduced during the reforming portion of the process a controlledquantity of a gas possessing a high specific gravity and a low ratio ofhydrogen to inerts. Such a gas 'maybe produced by the combustion of ahydrocarbon, preferably in the presence of insufficient air to supportcomplete combustion. An especially advantageous gas in this regard isthe product of incomplete combustion produced during the above-describedheat storage stage in presence of insufficient air to support completewhich a fluid hydrocarbon fuel is burned in the combustion. Thus, inaccordance with another embodiment of the present invention, at least aportion of the heating gases resulting from the combustion of the fluidhydrocarbon fuel in the presence of insufiicient air to support completecombustion during the heat storage portion of the cycle is mixed withthe gas produced during-the reforming portion of the cycle to provide amixed gas, which, when enriched as described, and blended with coke ovengas if desired, will meet the specifications required in the area wheremanufactured city gas is used, and which is, therefore, interchangeablewith the manufactured city gas. In accordance with thisembodiment,.while the products of incomplete combustion formed duringthe heat storage portion of the cycle may be led off to a storage vesselseparate from that to which the gas produced during the reformingportion of the cycle is led, it is preferred to lead the desiredquantity of products of incomplete combustion directly to a commonstorage vessel in the same manner as is the gas produced during thereforming portion of the cycle, that is, through conduit 13 by way ofconduit H and wash box l2.

The exact proportions of enriching gas, and products of combustion ifused, and coke oven gas if used, mixed with the gas produced during thereforming portion of the cycle to provide a finished gas suitable fordistribution as city gas are subject to variation, depending not onlyupon the specifications to be met, but also upon the exactcharacteristics of the enriching gas, and of the gas produced during thereforming portion of the cycle, and also of the products of combustionand coke oven gas if used. Generally manufactured city gases have acalorific value of between about 520 and about 570 B. t. u., a specificgravity of between about .45 and about .75 and a ratio of hydrogen toinerts of from 1 to 1 up to about 6 to 1. On the other hand, the gasproduced during the reforming portion of the cycle will have a calorificvalue lower than that recited above, for example, around 300 B. t. u., aspecific gravity within or somewhat below (for example .35) the rangerecited above, and a ratio of hydrogen to inerts within or somewhatabove (for example, 10 to 1) the range set forth above. The enrichinggas will have a calorific value well above that required, natural gashaving a heating value around 1050 B. t. u., a specific gravity around.6l-.63, and a hydrogen to inerts ratio of zero, since it is usuallyfree of hydrogen. The product of incomplete combustion will have acalorific value well below the above-recited range and may even be lessthan 100 B. t. u.; its specific gravity will be above the recited rangeoften being around 1, and its hydrogen to inerts ratio will be wellbelow the recited range.

It will be seen that although the proportions of the various gases thatare to be mixed may vary widely, the determination of the exactproportions needed in any particular case will offer no difiiculty tothose familiar with the gas-making art, and can be arrived at by simplecalculation. By varying the proportions of reactants, namely gaseoushydrocarbon and steam, or gaseous hydrocarbon, steam and .air, usedduring the reforming portion of the cycle, the various characteristicsof the resulting gas can be controlled as desired. In addition to thesevariables, by varying the amount of products of combustion, such as theproducts of incomplete combustion formed during the heat-storage portionof the cycle, which may be mixed with the gas produced during thereforming period, further controlof the characteristics of resultingmixed gas is afforded. In any event, it will be seen that the, presentinvention offers a process of wide flexibility to produce gasinterchangeable with any manufactured city gas, or suitable foradmixture with other gases, to meet changing situations encountered inthe city gas industry.

The broader aspects of the invention as well as the above-describedpreferred embodiments will be better understood from a consideration ofthe following specific examples which are given for purposes ofillustration and are not intended to limit the scope of the invention inany way.

Example I The reactor employed is the superheater shellof a conventionalcarburetted water gas set, the generator and carburetter being blankedoff andthe fuel, air, steam and hydrocarbon reactant be ing admitted tothe base of the superheater as shown in the drawing. The reactorcontains 144- cubic feet of randomly arranged silicon carbide pieces ata depth of 2 feet, 3 inches supported ona firebrick arch as shown in thedrawing, and 305 cubic feet of nickel-impregnated refractory bodiessupported on a firebrick arch as shown in the drawing.

A 1.5 minute cycle was employed, 44% of which was a heat storage period,51% of which was a reforming period and 5% of which was a steam purge.

During the heat storage period air and natural gas were admitted to thecombustion chamber at the rates of 8394 cubic feet per minute and 1000cubic feet per minute respectively. At this rate the air wasinsufficient for complete combustion. The hot combustion products flowedserially through the heat storage zone and catalyst zone and out thestack to the atmosphere.

During the reforming period natural gas, steam and air were mixed andadmitted to the space below the preheating zone at the following rates:natural gas, 2170 cubic feet per minute; steam, 143 pounds per minute;and air, 4197 cubic feet per minute. These gases passed through the heatstorage zone becoming heated to reaction temperatures and thence throughthe catalytic zone where reformation took place. The reformed gases wereled, by way of a wash box, to storage.

During the purge, steam was admitted to the combustion chamber at therate of 266 pounds per minute forcing residual reformed gases tostorage.

The cycles continued over a 24 hour period, the average temperaturesduring this period throughout various parts of the reactor being asfollows:

Bottom of heat-storage zone 1482 Top of heat-storage zone 1750 Bottom ofcatalytic zone 1780 Top of catalytic zone 1545 The gas produced duringthe reforming period had the following analysis and characteristics:

Illuminants per cent 0 CO do 14 H2 do 41.6 CO2 do 4.4 CH4 do 5 CzHs(10.... 2.7 Oz (30.... 0.5 N; do 31.8 B. t. u. per cubic foot 279Specific gravity .602 Hz/inerts ratio 1.16

With this gas was mixed suflicient natural gas having a heating value of1039 B. t. u. per cubic foot to provide a mixed gas having a heatingvalue of 530 B. t. u. per cubic foot. The mixture consisted of 67% ofthe above gas and 33% of natural gas and possessed, besides a heatingvalue of 530 B. t. u. per cubic foot, a specific gravity of .607 and ahydrogen to inerts ratio of 1.11.

Example II In this example, the same apparatus as that used in Example Iwas employed. The cycle, however, was a three minute cycle, 34% of whichwas a heat storage period in which the combustion products passed outthe stack to the at mosphere; 16% of which was a heat storage period inwhich natural gas was burned with in sufficient air to support completecombustion and the resulting products of incomplete combustion were ledoff to storage by way of the wash box; 45% of which was a reformingperiod, and of which was a steam purge.

During the heat storage period in which the combustion products weredirected out the stack to the atmosphere, air and natural gas wereadmitted to the combustion chamber at the rate of 10,773 and 1000 cubicfeet per minute, respectively, and burned. During the heat storageperiod in which products of incomplete combustion were led to storage,air and natural gas were admitted to the combustion chamber atthe rateof 8563 and 930 cubic feet per minute, re-

spectively, and burned.

During the reforming period natural gas, steam, and air were'aclmittedto the space before the heat storage zone at the following rates:natural gas, 2500 cubic feet per minute; steam, 220 pounds per minute,and air, 1575 cubic feet per minute. During the purge 231 pounds ofsteam per minute were admitted to the combustion chamber forcingresidual reformed gas to storage.

The cycles continued over a 24 hour period, the average temperaturesduring this period throughout various parts of the reactor being asfollows:

F. Bottom of heat-storage zone 1798 Top of heat-storage zone 1859 Bottomof catalytic zone 1755 Top of catalytic zone n 1478 The mixed gasproduced as the result of the reforming period and the heat storageperiod in which partial combustion products were led to storage had thefollowing analysis and charac- With this gas was mixed sufficientnatural gas having a heating value of 1034 B. t. u. per cubic foot toprovide a mixed gas having a heating value of 530 B. t. u. per cubicfoot. To provide this, a mixture consisting of 33.5% of natural gas and66.5% of the above-described gas was necessary. This mixture possessed,besides a heating value of 530 B. t. u. per cubic foot, a specificgravity of .61 and a hydrogen to inerts ratio of 1.02.

Example III Using the same apparatus as that employed in Examples I andII, a three minute cycle was employed, 59% of which was a heat storageperiod in which the fuel was burned in the presence of insuiiicient airto support complete combustion and the resulting products of combustionwere 14 led off to storage by way 01- the wash box;- 36% ofwhich wasreforming period, and 5% of which was a steam purge.-

During the heatstorage period, air and natus ral gas were admitted tothe combustion chamber at the rates of 5865 and 662 cubic feet perminute, respectively, and burned. During the reforming period naturalgas, steam and air were admitted to the space before the heat storagezone at. the following rates; natural gas, 2400 cubic feet per minute;steam, 180 pounds per minute; and air, 105.0, cubic feet per minute.During the p;urge,,200 pounds of steam per minute were admitted to thecombustion chamber, forc-v ing residual reformed gas to storage andelimimating any danger of havin an explosive mixture present. at thbeginni f f ll win heat storage step.

The cycles continued over a 24 hour period, the average t mperaturesduring t s period throughout the various p r s f h p tus being asfollows:

. F. Bottom of heat-storage zone 1762 Top of heat-storage zone 1822Bottom of catalytic zone 1897 Top of catalytic zone 1452 The mixed gasproduced as the result of the reforming period and the heat storageperiod were led to storage, and it will be noted that at no time is gasvented to the atmosphere. The resulting mixed gas bad the followinganalysis and characteristics:

In order to increase the heating value of this gas up to that requiredin the particular instance, natural gas having a heating value of 1034B. t. u. per cubic foot was mixed with it such that the natural gasamounted to 37.8% of the resulting gas mixture. This enriched gasmixture possessed, besides 'a heating value of 530 B. t. u. a

specific gravity of .68, and the ratio of hydrogen to inerts remained at.52.

This enriched gas was then mixed'with coke oven gas having a heatingvalue of 530 B. t. 11. per

cubic foot, a specific gravity of .48 and a ratio of hydrogen to inertsof 3.72, in an amount sumcient to raise its ratio of hydrogen to inertsto 1.1. This required 22 parts by volume of coke oven gas for each partsby volume of the enriched gas.

The final gas mixture then possessed a heating value of 530 B, t. u. percubic foot, 2. specific ravity of .662 and was distributed as city gas.

Considerable modification is possible in the selection of the gaseoushydrocarbon reactant, fuel gas, and blending gases, as well as in theprop-ortions. of reactants and b e ded ca e w th ut departins f om thescope o t inv nti n.

1. laim:

1. The cyclic process for the manufacture of a component of acombustible gas suitable for distribution in city gas systems whichcomprises, in one part of the cycle, burning a fluid fuel and passingthehot products of combustion through a bed of heat storage, material tostore heat therein, then through a bedof catalyst for the endothermicreaction between gaseous hydrocarbons and steam to store heat therein,at least the latter portion of said burning being conducted in thepresence of insufficient air to support complete combustion; and, duringanother part of the cycle, passing a normally gaseous hydrocarbon andsteam through said bed of heat storage material to heat said gases;passing the hot gases through said catalyst bed at a temperature toeffect conversion thereof to hydrogen and oxides of carbon, mainlycarbonmoncxide, and effecting in said catalyst bed conversion of saidhot gases into a gas rich in hydrogen and carbon oxides, mainly carbonmonoxide, and containing only a relatively small amount of hydrocarbons,and collecting the resulting gas.

2. The process of claim 1, wherein, during said conversion period, airis passed through said bed of heat storage material and catalyst bedwith said gaseous hydrocarbon and steam, and wherein said catalystcomprises nickel.

3. The cyclic process for the manufacture or" a component of acombustible gas suitable for distribution in city gas systems whichcomprises, in one part of the cycle, burning a fluid fuel in thepresence of insufficient air to support complete combustion; passing thehot products of incomplete combustion through a bed of heat storagematerial to store heat therein, then through a bed of catalyst for theendothermic reaction between gaseous hydrocarbons and steam to storeheat therein; and, in another part of the cycle, passing a normallygaseous hydrocarbon and steam through said bed of heat storage materialto heat said gases; passing the hot gases through said catalyst bed at atemperature to effect conversion thereof into hydrogen and oxides ofcarbon, mainly carbon monoxide, and effecting in said catalyst bedconversion of said hot gases into a gas rich in hydrogen and carbonoxides, mainly carbon monoxide, and containing only a relatively smallamount of hydrocarbons, and collecting the resulting gas.

4. The processor claim 3 wherein, during the said conversion period, airis passed through said bed of heat storage material and catalyst bedwith said gaseous hydrocarbon and steam, and wherein the catalystcomprises nickel.

5. The cyclic process for the manufacture of a component of acombustible gas suitable for distribution in city gas systems whichcomprises, in one part of the cycle, first burning a fluid fuel in thepresence of excess air and passing the hot products of combustionthrough a bed of heat storage material to store heat therein, and thenthrough a bed of catalyst for the endothermic reaction between gaseoushydrocarbons and steam to store heat therein; then burning a fluid fuelin the presence of insufficient air for complete combustion, and passingthe resulting hot products of incomplete combustion serially throughsaid bed of heat storage material and said catalyst bed to store furtherheat therein; and, during another part of the cycle, passing a normallygaseous hydrocarbon and steam through said bed of heat storagematerialto heat said gases; passing said hot gases through said catalystbed at a temperature to eifect conversion thereofinto hydrogen andoxides of carbon, mainly carbon monoxide, and efiecting in said catalystbed conversion of said hot gases into a gas rich in hydrogen and 16carbon oxides, mainly carbon monoxide, and containing only a relativelysmall amount of hydrocarbons, and collecting the resulting gas.

6. The process of claim 5, wherein, during said conversion period, airis also passed through said bed of heat storage material and catalystbed with said gaseous hydrocarbon and steam, and wherein said catalystcomprises nickel,

'7. The process of claim 5 wherein that portion of the heat storage partof the cycle during which excess air is employed for the combustion ofthe fuel makes up between about 15% and about 50% of the total heatstorage part of the cycle.

8. The process of claim 5 wherein the excess airemployed to burn thefluid fuel is between about 2% and about 50% in excess of that requiredfor complete combustion of the fuel.

9. The process of claim 5 wherein that portion of the heat storage partof the cycle during which excess air is employed for th combustion ofthe fuel makes up between about 15% and about 58% of the total heatstorage part of the cycle; and wherein the excess air employed to burnthe fuel is between about 2% and about 50% in excess of that requiredfor complete combustion of the fue 10. The cyclic process for themanufacture of a component of a combustible gas suitable fordistribution in city gas systems which comprises, in one part of thecycle, burning a fluid hydrocarbon fuel and passing the hot products ofcombustion through a bed of heat storage material to store heat thereinthen through a bed of catalyst for the endothermic reaction betweengaseous hydrocarbons and steam to store heat therein, at least thelatter portion of said burning being conducted in the presence ofinsufiicient air to support complete combustion and leading at least aportion of the products of incomplete combustion leaving the catalystbed to storage; and, during another part of the cycle, passing anormally gaseous hydrocarbon and steam through said bed of heat storagematerial to heat said gases; passing the hot gases through said catalystbed at a temperature to efiect conversion thereof to hydrogen and oxidesof carbon, mainly carbon monoxide, and effecting in said catalyst bedconversion of said hot gases into a gas rich in hydrogen and carbonoxides, mainly carbon monoxide, and containing only a relatively smallamount of hydrocarbons leading the resulting gas to storage; andadmixing the latter with said products of incomplete combustion.

11. The process of claim 10 wherein, during said conversion period, airis passed through said bed of heat storage material and catalyst bedwith gaseous hydrocarbon and steam, and whereing the catalyst comprisesnickel.

12. The cyclic process for the manufacture of a component of acombustible gas suitable for distribution in city gas systems whichcomprises, in one part of the cycle, burning a fluid hydrocarbon fuel inthe presence of insuflicient air to support complete combustion; passingthe hot products of incomplete combustion through a bed of heat storagematerial to store heat therein, then through a bed of catalyst for theendothermic reaction between gaseous hydrocarbons and steam to storeheat therein, and then leading at least a portion of said products ofincomplete combustion to storage; and, in another part of the cycle,passing a normally gaseous hydrocarbon and steam through said bed ofheat storage material to heat said gases; passing the hot gases throughsaid catalyst bed at a temperature to effeet conversion thereof intohydrogen and oxides of carbon, mainly carbon monoxide, and effectin insaid catalyst bed conversion or said hot gases into a gas rich inhydrogen and carbon oxides, mainly carbon monoxide, and containing onlya relatively small amount of hydrocarbons leading the resulting gas tostorage; and admixing the latter with said products of incompletecombustion.

13. The process of claim 12 wherein, during said conversion period, airis passed through said bed of heat storage material and catalyst bedwith said gaseous hydrocarbon and steam, and wherein the catalystcomprises nickel.

14. The cyclic process for the manufacture of a component of acombustible gas suitable for distribution in city gas systems whichcomprises, in one part of the cycle, first burning a fluid hydrocarbonfuel in the presence of excess air and passing the hot products ofcombustion through a bed of heat storage material to store heat therein,then through a bed of catalyst for the endothermic reaction betweengaseous hydrocarbons and steam to store heat therein, and then to theatmosphere; then burning a fluid hydrocarbon fuel in the presence ofinsufiicient air for complete combustion, passing the resulting hotproducts of incomplete combustion serially through said bed of heatstorage material and said catalyst bed to store further heat therein,and then passing at least a portion of said products of incompletecombustion to storage; and, in another part of the cycle, passing anormally gaseous hy drocarbon and steam through said bed of heat storagematerial to heat said gases; passing said hot gases through saidcatalyst bed at a temperature to eilect conversion thereof to hydrogenand oxides of carbon, mainly carbon monoxide, and effecting in saidcatalyst bed conversion of said hot gases into a gas rich in hydrogenand carbon oxides, mainly carbon monoxide, and containing only arelatively small amount of hydrocarbons; directing the resulting gas tostorage and admixing the latter with said products of incompletecombustion.

15. The process of claim 14 wherein, during said conversion period, airis also passed through said bed of heat storage material and catalystbed with said gaseous hydrocarbon and steam, and wherein said catalystcomprises nickel.

16. The process for the manufacture of a combustible gas suitable fordistribution in a city gas distribution system serving appliancesadjusted for the burning of manufactured gas of predetermined burningcharacteristics which comprises preparing gases in a cyclic process inwhich, in one part of the cycle, a fluid hydrocarbon fuel is burned andthe hot products of combustion are passed through a bed of heat storagematerial to store heat therein and then through a bed of catalyst forthe endothermic reaction between gaseous hydrocarbons and steam to storeheat therein, at least the latter portion of said burning beingconducted in the presence of insufiicient air to support completecombustion and leading at least a portion of the products of incompletecombustion leaving the catalyst bed to storage, and, in another part ofwhich cycle, a normally gaseous hydrocarbon and steam are passed throughsaid bed of heat storage material to heat said gases and then throughsaid catalyst bed at a temperature to eiTect conversion thereof intohydrogen and oxides of carbon, mainly carbon monoxide, and effecting insaid catalyst bed conversion of said hot gases into a gas rich inhydrogen and carbon oxides, mainly carbon monoxide and containing only arelatively small amount of hydrocarbons; mixing the resulting gas withsaid products of incomplete combustion and with a gas having a calorificvalue higher than that desired in the resulting mixture in proportionsto provide a mixed gas possessing burning characteristics comparable tothe predetermined burning characteristics of said manufactured gas,whereby the resulting gas may be distributed in said city gasdistribution system.

JOHN HAWLEY TAUSSIG, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,972,898 Odell Sept. 11, 1934 2,071,286 Johnson et al Feb.16, 1937 2,361,584 Allen Oct. 31, 1944 2,407,371 Jahnig Sept. 10, 1946FOREIGN PATENTS Number Country Date 357,956 Great Britain Sept. 29, 1931OTHER REFERENCES American Gas Association, "Fuel Flue Gases," 1940, page24.

1. THE CYCLIC PROCESS FOR THE MANUFACTURE OF A COMPONENT OF ACOMBUSTIBLE GAS SUITABLE FOR DISTRIBUTION IN CITY GAS SYSTEMS WHIHCOMPRISES, IN ONE PART OF THE CYCLE, BURNING A FLUID FUEL AND PASSINGTHE HOT PRODUCTS OF COMBUSTION THROUGH A BED OF HEAT STORAGE MATERIAL TOSTORE HEAT THEREIN, THEN THROUGH A BED A CATALYST FOR THE ENDOTHERMICREACTION BETWEEN GASEOUS HYDROCARBONS AND STEAM TO STORE HEAT THEREIN,AT LEAST THE LATTER PORTION OF SAID BURNING BEING CONDUCTED IN THEPRESENCE OF INSUFFICIENT AIR TO SUPPORT COMPLETE COMBUSTION; AND, DURINGANOTHER PART OF THE CYCLE, PASSING A NORMALLY GASEOUS HYDROCARBON ANDSTREAM THROUGH SAID BED OF HEAT STORAGE MATERIAL TO HEAT SAID GASES;PASSING THE HOT GASES THROUGH SAID CATALYST BED AT A TEMPERATURE TOEFFECT CONVERSION THEREOF TO HYDROGEN AND OXIDES OF CARBON, MAINLYCARBON MANOXIDE, AND EFFECTING IN SAID CATALYST BED CONVERSION OF SAIDHOT GASES INTO A GAS RICH IN HYDROGEN AND CARBON OXIDES, MAINLY CARBONMONOXIDE, AND CONTAINING ONLY A RELATIVELY SMALL AMOUNT OF HYDROCARBONS,AND COLLECTING THE RESULTING GAS.